Hopper lives in a pet shop with his sibling Pup and Pinkie. They miss their mother (whose parting words were "Find the mews") but figure they are going to homes eventually. One day, a boy comes in with a snake, and they realize they are to be sold as snake chow, so they escape. They end up in the train tunnels under Brooklyn and are soon separated. Hopper is rescued by Zucker, who is the son of the king of Atlantia. Everyone who meets Hopper is a bit in awe of him, and he soon realizes that he bears a resemblance to the former leader of the Mus, Dodger. Unfortunatley, Atlantia fights with the Mus, although Zucker seems to be at odds with his father over the refugee camps. When Hopper runs away to find his siblings, his loyalties become divided: He wants to side with Atlantia but also begins to believe that the camps are evil, he loves his sister Pinkie but is at odds with her because she has taken the position of Chosen One for the Mus until his arrival, and he's not sure if Firren, a ferocious but beautiful mouse, is good or evil. The book ends with enough questions that there is sure to be a sequel!

This book had lots of action and adventure, good plot twists, and shades of gray instead of black and white, which I always enjoy. Firren and Pinkie are both swashbuckling heroines, and the illustrations that accompany the text are a good addition. (the ARC only had a few). Readers who enjoy animal books like the Warriors series will enjoy this, and there's enough sword fighting for Redwall fans as well.